The present invention relates to a rectangular monobloc optical lens and a manufacturing method thereof, especially to a monobloc glass lens having a concave and a convex aspherical surfaces with features of high performance and lower cost and a manufacturing method thereof. The lens is applied to mobile phones with cameras, or other cameras with image sensors such as Charge-Charged Device (CCD), or Complementary Metal-Oxide. Semiconductor (CMOS).
Due to fast progress of modern technology, electronics are getting more compact, light-weigh, and having multiple functions. While a lot of electronics such as digital cameras, PC cameras, network cameras, mobile phones or personal digital assistance are mounted with an image taking device. For easy carrying and requirements of users, the image taking device not only has good image quality, but also has compact size as well as low cost so that it can be used widely.
There are various materials for producing spherical lens. The glass lens is better for correcting chromatic aberration so that it is adapted widely. However, it's difficult to correct Aberrations such as aplanatism or astigmatism for the glass spherical lens with smaller F Number and wide angle. In order to improve such disadvantages, aspherical plastic lens or aspherical glass lens are applied on image taking devices for better image quality. Please refer to U.S. Pat. No. 6,031,670, Japanese Patent Application No. P2001-183578A, or Taiwanese Patent Application No. 573740. Yet the lens length of the optical lens disclosed above is still too long. For example, the lens disclosed in Japanese Patent Application No. P2001-183578A consists of two lens sets. The so-called 1g-1p lens includes a glass lens and a plastic lens while “2-g”, “2-p” respectively represent two sets of glass lens and plastic lens. The distance from the first surface of the first lens to the second surface of the second lens is larger or equal to 0.9f (d≦0.9f, f is focal length of the whole lens set). Thus the volume of camera lens can't be reduced. Neither can the manufacturing cost be reduced.
Moreover, manufacturing processes of a conventional aspherical lens with biconvex aspherical surfaces includes following steps: a block of molding glass is cut into a plurality of small units. Each of the units is grinded and polished so as to form a semi-product with biconvex surfaces or a spherical semi-product. Then the semi-product is set into a mold for lens for hot pressing. It's time and labor consuming to run the grinding and polishing processes. Thus the manufacturing cost is increased and the process can't be refined. Therefore, the requirements of compact size and light weight for electronics can't be satisfied and the applications of the lens are restricted.